Photographic developer



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PHOTOGRIAPHIG DEVELOPERS Filed July l5, 1938 '4 Sheets-Sheet 4 i 1 I 3 'iwf-5a /foabfx @FNS/7:7'

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Patented July 11, 1939 i UNITED sTATEs PHOTOGRAPHIC DEVELOPER Louis C. Jones, Greenwich, Robert Bowling Barnes, Stamford, and Garnet Philip Ham, 01d Greenwich, Conn., signora to American Cyanamid Company, New York, N. Y., a oorporation of Maine Appumion July 1s, 193s, sel-nr No. 21am ff (Raimi.

This invention relates to photographic developers, and more particularly to developers for photographic negatives which are capable of variation of contrast.

The ordinary type of photographic developer of which the Metal-hydroquinone types are the most common normally contain at least three types of ingredients; the actual developers such as Metol, hydroquinone and ,the like, protective agents against oxidation such as sodium sulflte, and a suitable alkali to produce'a pH suited for the particular developer. In addition, other ingredients such as restrainers, for example alkali metal bromides and in the case of tropical developers, sodium sulfate, may be present. Normally, a developer formula is balanced with regard to the three main ingredients in order to give good results and produce a satisfactory fidelity in reproducing the various gradations of light and shadow of the object photographed. When a curve is constructed having ordinates proportional to the density of the final developed negative, that is to say, the negative logarithm .of the transmission and with abscissae proportional to the logarithm of exposure, there should be a long, reasonably straight portion of the curve ln order to reproduce with reasonable fidelity various exposures within a certain range. With most modern developers, satisfactory fidelity is obtained, but a relatively large number of formulae are in use because-it is dllcult to change the characteristics of a particular formula without upsetting its balance.

A few years ago, a new alkali consisting of a mixture of alkaline substances, notably borates, was introduced by the' Eastman Kodak Company under the name Kodalk, and is covered by U. S. Patent No. 1,990,800. Four different formulae of the Eastman Kodak Company, namely Didi-l5, DIK-50, DK-60 and DK-76, have been formulated using the new alkali and claims have been rnade for ,Kodalki that contrast can be varied within wide limits by variation in the amount of alkali without upsetting the balance of the developer, thus producing results which give poor ildelity. This is an important advan-h tage as it makes possible the use of a relatively small number of formulae for a wide number of purposes since it is possible to vary the contrast within considerable limits by variation of the alkali component without requiring a complete recalculation of the entire formula.

While "Kodalk possesses the properties claimed for it to a considerable degree and thus represents a distinct advance over the use of standard alkalies such as sodium carbonate, in some formulae it leaves much to be desiredl Its change in' contrast is sometimes accompanied by a loss of fidelity. According to the present invention, it has been found that a new class of (cl. ias-as) bases which can be used to supply the alkaline reaction necessary for most photographic developers possesses the advantages of variation in contrast with variation in amount of the base, and in some formulae the best of them are superior in this respect to "Kodalk. l The compounds of the present invention are those of the very strong organic bases, namely, the quaternary ammonium compounds and the amidines. The Quaternary ammonium compounds may be used in the form of their freebases, but theI v tion in typical., Metol-hydroquinone developer formulae. The compounds are also useful in other types of developers such as those using p-phenylene diamine and glycine, but are of less importance with this Iclass of developers-which are normally used at low contrast to produce extreme fine grain. The invention will also be described in conjunction with curves showing the results of `densitometric measurements on exposed negatives which are illustrated on the drawings in which Fig. l represents curves with a DK-l type developer;

Fig. 2 is a series of curves with a DK-50 type developer;

Fig. 3 is a sexies of curves with a DK-SO type developer; i

Fig. 4 is a series of curves with a DK-76 type developer;

Fig. 5 is a series of curves with various developers using sodium carbonate as an alkali;

Fig. y6 is a series'oi curves with various developers using a 50%-50% mixture of sodium car bonate and guanidine carbonate as alkalies; and

Fig. 'l is a series of curves comparing Tetrone B and guanidine borate.

EXAMPLE 1 An ordinary DK- developer was made up as follows; l

Water cubic centimeters 500 Metol grams-- 2.85 Sodium sulte, des do 45.00 Kodalk e -do 11.25 Potassium bromide do 0.95

Sodium sulfate do.. 22.50

and ,a second batch was made up with guanidine .carbonate as follows:

This type of developer is intended for tropical development of general nlm, and has a pH of approximately 9.2. The amount of guanidine' carbonate used was sumcient to give a similar pH.

A third batch of developer was made up with five times the amount of "Kodalk and its pH measured 10.17. Thereupon a fourth developer was made up with an amount of guanidine carbonate sufficient to give a similar pH. This oontained slightly less than i'ive'times the weight of guanidine carbonate in the second developer. A photographic wedge made by the Eastman Kodak Company and having nine steps between light and dark arranged logarithmically, each step from dark to light representing a transmission 150%,that of the preceding step. was used to make exposures .on 35 mm. Eastman Kodak supersensitive panchromatic film. This iilm was chosen as being representative of a medium fast', long latitude panchromatic iilm which would show up lack of fidelity or excessive fogging rapidly and which is a type of film where variations in contrast produced by the developer are normally most necessary. All exposures were carefully calibrated using a Leitz enlarger with a 10 watt bulb and lens stopped down to F12.5 as a source of illumination. All conditions of development including time, temperature, agitation, fixing. washing and the like were kept uniform and the only dierence between the tests was the developer type used. Densitometric measurements were made in a photoelectric densitometer calibrated against the wedge used for the exposures. The results appear on the curves in Fig. l of the drawings. It will be noted that in this ultra high speed tropical developer, both Kodalk and guanidine carbonate gave excellent results, both in normal amounts and when five times normal amounts were used. A. sharp increase in the contrast as shown by the greater steepness of the curve was observed but the straight portions of both sets of curves assure satisfactory fidelity.

A test was then made of the keeping qualities of the developers having ve times the amount Y of base and here a very sharp difference was noted. The guanidine carbonate after 20 days showed results substantially similar to a fresh normal guanidine carbonate developer, whereas the Kodalk had lost its fidelity and gave a curve of irregular shape.

ExAxPLl 2 Fm'mula 1 Water cubic centimeters-- 500 Metol grams-- 1.25 Sodium sulfite, des do- 15.00 Hydroquinone do- 1.25 Kodalk" do 5.00 Potassium bromide do 0.25

Formula 2 Water cubic centimeters-- 500 Metal grams 125 Sodium sulflte, des do 15.00 Hydroquinone Q do 1.25 Guanidine carbonate do 3.30 Potassium bromide do.. 0.25

This formula is one used for the development of normal films of both orthochromatic and panchromatic type. The results obtained are shown in the curves of Fig. 2 from which itis apparent "that the contrast with guanidine carbonate is EXAMPLE 3 Four developers were prepared according to Eastman Kodak formula DK-SO as follows, the first having the normal amount of Kodalk" and giving a pH of 9.43, the second having the required amount of guanidine carbonate to give the same pH. and two others. one of which contained ve times the amount of Kodalk and the other an amount of guanidine carbonate which gave a slightly higher pH. The actual amount used was only i1/2 times as much as that.

used in the normal solution.

Formula 1 Water cubic centimeters-- 500 Metol grams 1.25 Sodium sulte, des do 15.00 Hydroquinone do 1.25 Kodalk do 10.00 Potassium bromide do 0.25

Formula 2 Water cubic centimeters-- 500 Metol grams-- 1.25 Sodium sulflte, des do 15.00 Hydroquinone do 1.25 Guanidine carbonate do 6.80 Potassium bromide i do 0.25

This developer is also intended for general development of lms of both the orthochromatic and panchromatic type where a somewhat higher contrast is desired. 'I'he results are shown in Fig.

3. Again it will be noted that the increase in contrast is substantially the same with guanidine carbonate and with Kodalk" but on keeping, the "Kodalk loses fidelity whereas the guanidine carbonate assumes 'a position intermediate between that of the fresh normal developer and that of the fresh developer with five times the base. The curve, however, shows a long straight portion retaining the excellent fidelity characteristics which are typical of the guanidine carbonate developers.

Exnnu4 Four developers were prepared according to Eastman Kodak formula DK-76 as follows, the ilrst `.having the normal amount of Koda1k" and giving a. pH of 8.51, the second having the required amount of guanidine carbonate to give the same -pH and two others, one of which contained five times the amount oi' Kodalk" and the other amount of guanidine carbonate which gave a slightly higher pH. 'I'he actual amount used was slightly more than five times as much as that used in the normal solution. 'I'his was necessary because of the shape of the pH curve of guanidine carbonate at lower concentrations.

The results are shown on the curves of Fig; 4;

The guanidine carbonate gave somewhat greater contrast than Kodalk, but in this developer the keeping qualities of the Kodalk are improved.

Exmr.: 6

A surprising result is obtained when mixtures of guamdlne carbonate and sodium carbonate are used. The mixtures appear to have substantially the desirable characteristics of guanidine carbonate alone. The formula DK-50 type was prepared substituting the mixture for the ve times value in Example 2, and the results for various mixtures are shown in the curves in Fig. d which should be compared with the curve for sodium carbonate alone with DK-50 in Fig. 5. .It will be noted that while all of the curves show satisfactory fidelity, the good contrast with best ildelity is obtained with the 50%-50% mixture of guanidine carbonate and sodium carbonate. The particular proportions are, however, not critical which is an advantage. The possibility of substituting sodium carbonate for a considerable part of the guanidine carbonate represents a real commercial advantage because of the lower price of the sodium carbonate as contrasted with guanldine carbonate or with "Kodalk.

Exam La7 DK-50 and DK-76 formulae were prepared with ilve times normal Kodalk and with five times normal trimethyibenzylammonium hydroxide ("Tetrone 3). 13K-50 was also pre- .pared with ve times normal guanidine berate.

The results appear in Fig. 7. It will be noted that Tetrone B gave results similar to Kodalk" in the case of DK-50 with slightly less contrast but somewhat better delity. The results of the DK-76 show excellent fidelity but less contrast. Guanidine borate, due to its relative insolubility,

could not be used to produce the desired pH. The f developer solution produced a pH of only 8.8 in place of a normal 9.98. It will be noted that the YVcur've does not show as high contrast which, of

course, is to be expected as the necessary alkalinity could not be reached with this compound.

What we claim is:

1. A. photographic developer for silver halides containing as its alkalinity producing agent guanidine carbonate.

2. A metol-hydroquinone photographic developer containing -as its`alkalinity producing agent guanidine carbonate. y

3. A photographic developer containing as its alkalinity producing agent a mixture of sodium carbonate and guanidine carbonate in en'ective amounts.

4. A metal-hydroquinone photographic developer containing as its alkalinity producing agent a mixture of sodium carbonate and guanidine carbonate in effective amounts.

IDUIS C. JONES. ROBERT BOWLING BARNES. e G P 'if' il' HAM. 

